Gas turbine engine and frame

ABSTRACT

One embodiment of the present invention is a unique gas turbine engine. Another embodiment is a unique frame for a gas turbine engine. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines and gas turbine engine frames. Further embodiments, forms, features, aspects, benefits, and advantages of the present application shall become apparent from the description and figures provided herewith.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of, and claims priorityunder 35 USC §120 to, U.S. Non-Provisional Application 12/978,939, “GASTURBINE ENGINE AND FRAME” filed Dec. 27, 2010, the entire contents ofwhich are incorporated by reference, which is a non-provisionalapplication of, and claims priority under 35 USC §119(e) to, U.S.Provisional Application 61/291,592, “GAS TURBINE ENGINE AND FRAME” filedDec. 31, 2009, the entire contents of which are incorporated byreference.

GOVERNMENT RIGHTS

The present application was made with United States government supportunder Contract No. F33615-03-D-2357 awarded by the United Statesgovernment. The United States government may have certain rights in thepresent application.

FIELD OF THE INVENTION

The present invention relates to gas turbine engines, and moreparticularly, to gas turbine engine frames.

BACKGROUND

Structures such as frames for gas turbine engines remain an area ofinterest. Some existing systems have various shortcomings, drawbacks,and disadvantages relative to certain applications. Accordingly, thereremains a need for further contributions in this area of technology.

SUMMARY

One embodiment of the present invention is a unique gas turbine engine.Another embodiment is a unique frame for a gas turbine engine. Otherembodiments include apparatuses, systems, devices, hardware, methods,and combinations for gas turbine engines and gas turbine engine frames.Further embodiments, forms, features, aspects, benefits, and advantagesof the present application shall become apparent from the descriptionand figures provided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 schematically depicts a gas turbine engine having an intermediateframe in accordance with an embodiment of the present invention.

FIG. 2 is an exploded side view of an intermediate frame for a gasturbine engine in accordance with an embodiment of the presentinvention.

FIG. 3 is a cross section of the intermediate frame of FIG. 2.

FIGS. 4A and 4B are end views of the intermediate frame of FIG. 2.

DETAILED DESCRIPTION

For purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings, and specific language will be used to describe the same.It will nonetheless be understood that no limitation of the scope of theinvention is intended by the illustration and description of certainembodiments of the invention. In addition, any alterations and/ormodifications of the illustrated and/or described embodiment(s) arecontemplated as being within the scope of the present invention.Further, any other applications of the principles of the invention, asillustrated and/or described herein, as would normally occur to oneskilled in the art to which the invention pertains, are contemplated asbeing within the scope of the present invention.

Referring now to the drawings, and in particular, FIG. 1, a non-limitingexample of a gas turbine engine 10 in accordance with an embodiment ofthe present invention is depicted. Engine 10 includes a fan system 12,an intermediate frame 14, a compressor system 16, a combustor 18 and aturbine system 20. In one form, engine 10 is a multi-spool engine. Inother embodiments, engine 10 may be a single spool engine or amulti-spool engine having any number of spools. In one form, engine 10is a turbofan engine, wherein fan system 12 includes a plurality of fanstages (not shown). In other embodiments, engine 10 may be another typeof gas turbine engine, such as a turbojet engine, a turboshaft engine ora turboprop engine, or a turbofan engine having only a single fan stage.

Fan system 12 is operative to pressurize air received into engine 10,some of which is directed into compressor system 16 as core flow. Thebalance of the air pressurized by fan system 12 is directed into abypass duct system (not shown) and discharged by turbofan engine 10 togenerate thrust. In one form, fan system 12 includes two fan stages (notshown). In other embodiments, a greater or lesser number of fan stagesmay be employed.

Intermediate frame 14 is operative to direct air pressurized by fansystem 12 toward compressor system 16, and to transmit engine 10mechanical loads to an engine mount system 22, such as an intermediateengine mount. Although depicted as being disposed between fan system 12and compressor system 16, it will be understood that in otherembodiments intermediate frame 14 may take other forms and/or may belocated in other positions. For example, in other embodiments,intermediate frame 14 may be located between compressor 16 and combustor18; between combustor 18 and turbine system 20; and/or may be considereda portion of compressor system 16 or turbine system 20, and/or may houseall or a portion of one or more of fan system 12, compressor system 16,combustor 18 and turbine system 20.

Compressor system 16 is operative to compress the core flow dischargedby fan system 12. In one form, compressor system 16 includes twomulti-stage compressors (not shown), each of which includes a pluralityof blades and vanes in a plurality of stages for compressing airreceived by compressor system 16. In other embodiments, compressorsystem 16 may be in the form of a single multi-stage compressor. Instill other embodiments, compressor system 16 may include more than twocompressors, e.g., a low pressure (LP) compressor, an intermediatepressure (IP) compressor and a high pressure (HP) compressor.

Combustor 18 is in fluid communication with compressor system 16.Combustor 18 is operative add fuel and combust air pressurized bycompressor system 16.

Turbine system 20 is in fluid communication with combustor 18. Turbinesystem 20 operative to expand the hot gases received from combustor 18and to extract energy therefrom to drive compressor system 16 and fansystem 12. In one form, turbine system 20 includes two turbines, i.e.,an LP turbine and an HP turbine. In other embodiments, a greater orlesser number of turbines may be employed. Each turbine includes one ormore stages of blades and vanes.

Referring now to FIG. 2, an exploded view of a non-limiting example ofintermediate frame 14 is depicted and described. Intermediate frame 14includes a metallic inner hub 24, a metallic outer construction 26, acomposite flowpath 28, a metallic flange 30, a plurality of servicetubes 34, a plurality of metallic struts 32 and a plurality of strutcaps 36.

Metallic inner hub 24 is a structural component of intermediate frame 14and houses, for example, a bearing sump and a gearbox, for whichmetallic inner hub 24 provides structural support. In one form, thebearing sump includes mainshaft bearings, such as rolling elementbearings, that support all or part of one or more engine 10 rotors.Metallic inner hub 24 is formed of a metallic material, such as atitanium, aluminum or magnesium alloy.

Metallic inner hub 24 includes a plurality of strut pedestals 38 and acontoured outer surface 39. Strut pedestals 38 extend outward fromcontoured outer surface 39. In one form, strut pedestals 38 extendradially outward from contoured outer surface 39. In other embodiments,strut pedestals may extend outward from contoured outer surface 39 inother fashions, e.g., tangentially from contoured outer surface 39 ortangentially from a reference diameter. Strut pedestals 38 areconfigured for engagement with service tubes 34 and metallic struts 32.In one form, strut pedestals 38 and outer surface 39 are part of anintegral unit forming metallic inner hub 24. In other embodiments, strutpedestals 38 and/or outer surface 39 may be formed as separatecomponents and assembled together to form metallic inner hub 24. In oneform, outer surface 39 is generally parallel to an inner flowpath wallinside intermediate frame 14 (e.g., inner wall 52 of composite flowpath28, described below). In other embodiments, outer surface 39 may formpart of the inner flowpath surface.

Metallic outer construction 26 is formed of a metallic material, such asa titanium, aluminum or magnesium alloy. Metallic outer construction 26is adapted to interface with strut caps 36 and with engine mount system22. Metallic outer construction 26 is operative to maintain thecircumferential orientation of metallic struts 32 and service tubes 34.Metallic outer construction is also operative to transmit engine 10mechanical loads to engine mount system 22.

Composite flowpath 28 is radially disposed between metallic inner hub 24and metallic outer construction 26. Composite flowpath 28 is formed of acomposite material. In one form, the composite material is a carbonbismaleimide composite. A non-limiting example of a carbon bismaleimidecomposite is Cycom 5250-4 BMI, commercially available from CytecIndustries Inc., headquartered in Woodland Park, N.J., USA. Othercomposite materials may be used in other embodiments, e.g., includingceramic matrix composites, metal matrix composites, organic matrixcomposites and/or carbon-carbon composites. In one form, compositeflowpath 28 is formed via a resin transfer molding (RTM) process. Inother embodiments, other manufacturing processes and techniques suitablefor use in manufacturing composites may be employed in addition to or inplace of RTM. In one form, composite flowpath 28 has a cavity 42 adaptedto receive metallic inner hub 24.

Metallic flange 30 is adapted to interface with both composite flowpath28 and with metallic inner hub 24. Metallic flange 30 is operative tosecure composite flowpath 28 to metallic inner hub 24. Service tubes 34and metallic struts 32 of intermediate frame 14 extend between metallicinner hub 24, e.g., strut pedestals 38, and outer construction 26.Metallic struts 32 are formed of a metallic material, such as atitanium, aluminum or magnesium alloy. Engine mechanical loads, such asrotor loads, inertial loads and engine weight loads are reacted bymetallic inner hub 24 for transmission to engine mount system 22 viastrut pedestals 38. Strut pedestals 38 transmit the mechanical loadsfrom metallic inner hub 24 into metallic struts 32.

Strut caps 36 are adapted to interface with, service tubes 34 andmetallic outer construction 26, and may also include interface featuresfor connection to engine externals, such as tubing and a wiring harness.Metallic struts 32 transmit the mechanical loads to metallic outerconstruction 26 via strut caps 36. The loads are transmitted frommetallic outer construction 26 to mount system 22.

Strut pedestals 38 and strut caps 36 are adapted to interface withservice tubes 34. Service tubes 34, which may also be referred to astransfer tubes, provide passages between metallic inner hub 24 andmetallic outer construction 26 for the provision of services to and frommetallic inner hub 24. For example, in some embodiments, service tubes34 are structured to conduct one or more of pressurized lube oil,scavenge oil, seal charging air, sump vent air, cooling air, one or moresensors, one or more shafts, such as a tower shaft 40 for transmittingpower to an accessory gearbox, and/or one or more communications linksand/or power cables between metallic inner hub 24 and metallic outerconstruction 26. The communications links include, for example, wiredand/or optical links to transmit sensor data and/or control inputs, aswell as wired links to transmit electrical power. In one form, servicetubes 34 are fitted on either end into holes in metallic inner hub 24and strut caps 36, and are sealed, e.g., with an o-ring or gasket.

Referring now to FIGS. 3, 4A and 4B, the exemplary intermediate frame ofFIG. 2 is depicted as assembled. FIG. 3 is a cross section ofintermediate frame 14, and FIGS. 4A and 4B are end views of intermediateframe 14.

Composite flowpath 28 is disposed radially between metallic inner hub 24and metallic outer construction 26. Composite flowpath 28 definesflowpaths for the working fluid of engine 10. A flowpath is a passagewaythat channels bulk working fluid flow through engine 10, i.e., coreairflow and bypass airflow, as opposed to fluid passages that transmitrelatively small quantities of fluids, e.g., cooling air, pressurebalance air, vent air and seal charging air, such as service tubes 34.As illustrated in FIG. 3, composite flowpath 28 defines both a primaryflowpath 46 and a secondary flowpath 48. In other embodiments, a greateror lesser number of flowpaths may be defined by composite flowpath 28.In one form, secondary flowpath 48 is disposed radially outward ofprimary flowpath 46, although other arrangements may be employed inother embodiments. In one form, primary flowpath 46 is operative toconduct fan system 12 discharge flow to compressor system 16, andsecondary flowpath 48 is operative to conduct fan system 12 dischargeflow as a bypass flow.

Composite flowpath 28 includes a composite primary flowpath outer wall50 and a composite primary flowpath inner wall 52 spaced apart fromouter wall 50. Inner wall 52 is disposed radially inward of outer wall50. Outer wall 50 and inner wall 52 define primary flowpath 46.Composite flowpath 28 also includes a composite secondary flowpath outerwall 54 and a composite secondary flowpath inner wall 56 spaced apartfrom outer wall 54. Inner wall 56 is disposed radially inward of outerwall 54. Outer wall 54 and inner wall 56 define secondary flowpath 48.

Composite flowpath 28 includes a plurality of hollow composite struts44. Composite struts 44 are subdivided two groups: inner compositestruts 44A and outer composite struts 44B. In one form, inner compositestruts 44A and outer composite struts 44B are hollow. In otherembodiments, some or all of inner composite struts 44A and outercomposite struts 44B may be solid.

Composite struts 44A extend between composite primary outer wall 50 andcomposite primary inner wall 52. Composite struts 44A are adapted toreceive strut pedestals 38, metallic struts 32 and service tubes 34.Composite struts 44B extend between composite secondary flowpath outerwall 54 and composite secondary flowpath inner wall 56. Composite struts44B are adapted to receive metallic struts 32 and service tubes 34. Inone form, composite flowpath 28 is integrally formed as a unitary singlepiece structure, including outer wall 50, inner wall 52, outer wall 54,inner wall 56, and composite struts 44A and 44B. In other embodimentscomposite flowpath 28 may be in the form of discrete compositecomponents that are assembled together.

Composite flowpath 28 and metallic inner hub 24 are adapted to interfaceand transmit aerodynamic loads on composite flowpath 28 to metallicinner hub 24. For example, loads resulting from pressures and flows inprimary flowpath 46 and secondary flowpath 48 are transmitted tometallic inner hub 24. In addition loads resulting from the pressures incavities of composite flowpath 28, e.g., cavity 42 and a cavity 58disposed between primary flowpath outer wall 50 and secondary flowpathinner wall 56, are transmitted to metallic inner hub 24. In one form,composite struts 44A and strut pedestals 38 are adapted to jointly forman interface for transmitting aerodynamic loads from composite flowpath28 to metallic inner hub 24. In other embodiments, intermediate frame 14may be configured to transmit aerodynamic loads from composite flowpath28 to other structures, such as contoured outer surface 39 or a face ofmetallic hub 24, one or more of metallic struts 32 and/or metallic outerconstruction 26.

In one form, intermediate frame 14 is assembled by inserting innermetallic hub 24 into cavity 42 of composite flowpath 18. Compositeflowpath 28 is secured onto metallic inner hub 24 with metallic flange30. For example, in some embodiments, metallic flange 30 is bolted ontometallic inner hub 24 to clamp composite flowpath 28 between metallicinner hub 24 and metallic flange 30. Metallic struts 32 and servicetubes 34 are inserted into composite struts 44 for interface withmetallic inner hub 24, e.g., via strut pedestals 38. Strut caps 36 arethen installed over metallic struts 32 and service tubes 34. Metallicouter construction 26 is then assembled over strut caps 36 and securedto strut caps 36, e.g., using bolts (not shown).

Metallic inner hub 24, metallic struts 32 and metallic outerconstruction 26, as assembled, form a loadpath that transfers enginemechanical loads between metallic inner hub 24 and metallic outerconstruction 26, and from metallic outer construction to engine mountsystem 22. The loadpath passes through the metallic structures ofintermediate frame 14, and bypasses composite flowpath 28. By beingdivorced from the loadpath, composite flowpath 28 does not require thestrength of metallic materials, which allows the use of compositematerials to form flowpath 28, which may in some embodiments reduce theweight of intermediate frame 14 relative to similar structures formedsolely or primarily of metallic materials.

Embodiments envisioned include a gas turbine engine frame, including ametallic inner hub; a metallic outer construction; and a compositeflowpath disposed between the metallic inner hub and the metallic outerconstruction, the composite flowpath defining a primary flowpath for aworking fluid of the gas turbine engine.

In a refinement, the gas turbine engine frame also includes metallicstruts extending between the metallic inner hub and the metallic outerconstruction, wherein the metallic inner hub, the metallic struts andthe metallic outer construction are assembled to form a loadpath totransfer engine mechanical loads between the metallic inner hub and themetallic outer construction. In another refinement, the loadpathbypasses the composite flowpath. In a further refinement, the gasturbine engine frame is structured to transmit aerodynamic loads fromthe composite flowpath to one of the metallic inner hub, the metallicstruts and the metallic outer construction.

In another refinement, the composite flowpath is formed as a singlepiece structure.

In yet another refinement, the composite flowpath includes a compositeinner flowpath wall and a composite outer flowpath wall spaced apartfrom the composite outer flowpath wall, and wherein the composite innerflowpath wall and the composite outer flowpath wall define the primaryflowpath. In one form, the composite flowpath includes a plurality ofcomposite struts, wherein at least a portion of each composite strutextends between the composite inner flowpath wall and the compositeouter flowpath wall. In a refinement, the composite inner flowpath wall,the composite outer flowpath wall and the plurality of composite strutsare integrally formed.

Embodiments also include a gas turbine engine, including a compressor; aturbine; and an engine frame, the engine frame including a metallicload-bearing structure and a composite flowpath, wherein the metallicload-bearing structure defines a loadpath operative to transmit enginemechanical loads to an engine mount of the gas turbine engine, andwherein the composite flowpath is divorced from the loadpath.

In a refinement, the composite flowpath defines a primary flowpath for aworking fluid of the gas turbine engine. In a further refinement, thecomposite flowpath includes a primary flowpath outer wall and a primaryflowpath inner wall disposed radially inward of the primary flowpathouter wall, wherein the primary flowpath outer wall and the primaryflowpath inner wall define the primary flowpath.

In another refinement, the composite flowpath further defines asecondary flowpath for the working fluid of the gas turbine engine. Inone form, the composite flowpath includes a secondary flowpath outerwall and a secondary flowpath inner wall disposed radially inward of thesecondary flowpath outer wall, and wherein the secondary flowpath innerwall and the secondary flowpath outer wall define the secondaryflowpath. In a refinement, the composite flowpath includes a compositestrut extending through the secondary flowpath. In another refinement,the metallic load-bearing structure includes a metallic strut disposedwithin the composite strut, wherein the metallic strut is operative totransmit the engine mechanical loads through the secondary flowpath.

In another refinement, the metallic load-bearing structure includes ametallic inner hub disposed radially inward of the composite flowpath; ametallic outer construction disposed radially outward of the compositeflowpath; and a metallic strut extending between the metallic inner huband the metallic outer construction.

In yet another refinement, the gas turbine engine includes a servicetube extending between the metallic inner hub and the metallic outerconstruction, wherein the service tube is structured to conduct betweenthe metallic inner hub and the metallic outer construction at least oneof pressurized lube oil; scavenge oil, seal charging air; sump vent air,cooling air, a sensor, and a communications link. In one form, thecomposite flowpath includes a composite strut disposed at leastpartially around the service tube. In one form, the composite flowpathis formed as a single piece structure.

In still another refinement, the composite flowpath includes a compositestrut disposed at least partially around the metallic strut.

Embodiments also include a gas turbine engine, including a compressor; aturbine; and an engine frame, the engine frame including composite meansfor defining a primary flowpath for a working fluid of the gas turbineengine; and means for transmitting engine mechanical loads to an enginemount of the gas turbine engine, wherein the composite means aredivorced from the engine mechanical loads.

In a refinement, the engine frame also includes composite means fordefining a secondary flowpath for the working fluid of the gas turbineengine.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment(s), but on the contrary, is intended to covervarious modifications and equivalent arrangements included within thespirit and scope of the appended claims, which scope is to be accordedthe broadest interpretation so as to encompass all such modificationsand equivalent structures as permitted under the law. Furthermore itshould be understood that while the use of the word preferable,preferably, or preferred in the description above indicates that featureso described may be more desirable, it nonetheless may not be necessaryand any embodiment lacking the same may be contemplated as within thescope of the invention, that scope being defined by the claims thatfollow. In reading the claims it is intended that when words such as“a,” “an,” “at least one” and “at least a portion” are used, there is nointention to limit the claim to only one item unless specifically statedto the contrary in the claim. Further, when the language “at least aportion” and/or “a portion” is used the item may include a portionand/or the entire item unless specifically stated to the contrary.

What is claimed is:
 1. A gas turbine engine frame, comprising: ametallic inner hub; a metallic flange; a metallic outer construction;and a composite flowpath structure comprising a primary flowpathstructure disposed between the metallic inner hub and the metallic outerconstruction, wherein the composite flowpath structure includes at leastone of carbon bismaleimide composites, ceramic matrix composites, metalmatrix composites, organic matrix composites or carbon-carboncomposites, and wherein the metallic flange is configured to secure thecomposite flowpath structure to the metallic inner hub; wherein theprimary flowpath structure comprises a primary composite outer flowpathwall and a primary composite inner flowpath wall spaced radially apartfrom the primary composite outer flowpath wall, and the primarycomposite outer flowpath wall and the primary composite inner flowpathwall together define the primary flowpath structure for a working fluidof the gas turbine engine; and wherein the composite flowpath structurefurther comprises a plurality of inner composite struts, wherein atleast a portion of each inner composite strut extends between theprimary composite inner flowpath wall and the primary composite outerflowpath wall.
 2. The gas turbine engine frame of claim 1, furthercomprising metallic struts extending between the metallic inner hub andthe metallic outer construction, wherein the metallic inner hub, themetallic struts and the metallic outer construction are assembled toform a loadpath to transfer engine mechanical loads between the metallicinner hub and the metallic outer construction.
 3. The gas turbine engineframe of claim 2, wherein the loadpath bypasses the composite flowpathstructure, and wherein the composite flowpath structure is configured tobe divorced from mechanical loads transferred between the metallic innerhub and the metallic outer construction.
 4. The gas turbine engine frameof claim 2, wherein the gas turbine engine frame is structured totransmit aerodynamic loads from the composite flowpath structure to oneof the metallic inner hub, the metallic struts and the metallic outerconstruction.
 5. The gas turbine engine frame of claim 1, wherein thecomposite flowpath structure is formed as a single piece structure. 6.The gas turbine engine frame of claim 1, wherein the composite flowpathstructure and the plurality of inner composite struts are integrallyformed.
 7. The gas turbine engine frame of claim 1, wherein thecomposite flowpath structure includes a secondary flowpath structuredisposed radially outward of the primary flowpath structure, wherein thesecondary flowpath structure includes a secondary composite innerflowpath wall spaced radially apart from a secondary composite outerflowpath wall to define the secondary flowpath structure for workingfluid of the gas turbine engine; and a plurality of outer compositestruts wherein at least a portion of each outer composite strut extendsbetween the secondary composite inner flowpath wall and the secondarycomposite outer flowpath wall.
 8. A gas turbine engine, comprising: afan system; a compressor; a turbine; and an engine frame, the engineframe disposed between the fan system and the compressor, the engineframe including a metallic load-bearing structure and a compositeflowpath structure, wherein the composite flowpath structure is aseparate component from the metallic load-bearing structure, wherein themetallic load-bearing structure defines a loadpath operative to transmitengine mechanical loads to an engine mount of the gas turbine engine,and wherein the composite flowpath structure is divorced from theloadpath, wherein the composite flowpath structure includes at least oneof carbon bismaleimide composites, ceramic matrix composites, metalmatrix composites, organic matrix composites or carbon-carboncomposites; wherein the composite flowpath structure includes a primarycomposite inner wall spaced apart from a primary composite outer wall todefine a primary inner flowpath structure for a working fluid of the gasturbine engine; wherein the composite flowpath structure further definesa secondary flowpath structure for the working fluid of the gas turbineengine; and wherein the secondary flowpath structure includes asecondary composite outer wall and a secondary composite inner walldisposed radially inward of the secondary composite outer wall.
 9. Thegas turbine engine of claim 8, wherein the composite flowpath structureincludes a composite strut extending through the secondary flowpathstructure.
 10. The gas turbine engine of claim 9, wherein the metallicload-bearing structure includes a metallic strut disposed within thecomposite strut, and wherein the metallic strut is operative to transmitthe engine mechanical loads through the secondary flowpath structure.11. The gas turbine engine of claim 8, wherein the metallic load-bearingstructure includes: a metallic inner hub disposed radially inward of thecomposite flowpath structure; a metallic outer construction disposedradially outward of the composite flowpath structure; and a metallicstrut extending between the metallic inner hub and the metallic outerconstruction.
 12. The gas turbine engine of claim 11, further comprisinga service tube extending between the metallic inner hub and the metallicouter construction, wherein the service tube is structured to conductbetween the metallic inner hub and the metallic outer construction atleast one of: pressurized lube oil; scavenge oil; seal charging air;sump vent air; cooling air; a sensor; and a communications link.
 13. Thegas turbine engine of claim 12, wherein the composite flowpath structureincludes a composite strut disposed at least partially around theservice tube.
 14. The gas turbine engine of claim 11, wherein thecomposite flowpath structure includes a composite strut disposed atleast partially around the metallic strut.
 15. The gas turbine engine ofclaim 8, further comprising at least one composite strut extendingbetween the spaced apart composite primary flowpath structure walls. 16.The gas turbine engine of claim 8, wherein the metallic load-bearingstructure includes an engine mount and a metallic inner hub, and whereinthe composite flowpath structure is configured to be divorced fromengine mechanical loads transmitted from the metallic inner hub to theengine mount.
 17. A gas turbine engine, comprising: a compressor; aturbine; and an engine frame, the engine frame including: inner andouter primary composite walls defining a composite primary flowpathstructure for a working fluid of the gas turbine engine, wherein thecomposite primary flowpath structure includes at least one of carbonbismaleimide composites, ceramic matrix composites, metal matrixcomposites, organic matrix composites or carbon-carbon composites; ameans for transmitting engine mechanical loads to an engine mount of thegas turbine engine, wherein the means for transmitting engine mechanicalloads includes an inner metallic hub, wherein the composite primaryflowpath structure is a separate component from the metallic inner hub,wherein a metallic flange secures the composite flowpath structure tothe metallic inner hub, and wherein the composite primary flowpathstructure is divorced from the engine mechanical loads; and inner andouter secondary composite walls defining a secondary flowpath structurefor a working fluid of the gas turbine engine; wherein the secondaryflowpath structure is positioned radially outward of the primaryflowpath structure.
 18. The gas turbine engine of claim 17, furthercomprising an inner composite strut connected between the inner andouter primary composite walls; and an outer composite strut connectedbetween the inner and outer secondary composite walls.
 19. The gasturbine engine of claim 17, wherein the primary flowpath structure andthe secondary flowpath structure are configured to be divorced fromengine mechanical loads transferred from the inner metallic hub to theengine mount.